The present invention relates to the transmission of optical signals and, more particularly, to a method and article of manufacture pursuant to the method, wherein chips and/or electronic circuit components are fabricated with embedded optical cables for transmitting optical and electrical signals.
The need for operating circuits with higher clock speeds and for improving the quality of electrical transmission signals has given rise to the use of optical circuits and methods. The optical transmission of electrical signals offers some distinct advantages over transmitting the signals by electrical wiring, to wit: optical circuits are scalable to higher clock speeds; optical circuits do not suffer from frequency or distance-dependent signal distortion; and optical signals have low dissipation. Most importantly, optical circuits can provide greater bandwidth.
The different components of optical circuitry comprise emitters to convert electrical signals from the chips to optical signals, detectors to convert from optical signals to electrical signals, and mirrors/lenses, waveguides, or fiber optics cables for transmitting the optical signals.
There are two key requirements for successfully implementing optical methods and components into an electrical circuit environment: developing efficient manufacturing techniques for implementing and incorporating the optical components within the electrical circuit in a cost effective manner; and developing ways to densely pack optical components into an array and upon a laminate in order to match or exceed the electrical performance of present day electronic chips.
There are currently two ways to transfer an optical signal: use waveguides (typically made of polyimides or silicon based materials) or utilize fiber optic cables. To incorporate a waveguide into a laminate requires additional fabrication steps that can drastically increase the costs of manufacture.
The present invention involves a low cost method of incorporating fiber optic cables within organic laminates such as ball grid array (BGA) circuit laminate. The optical fibers of this invention are embedded within these organic laminates during the lamination process, so no additional fabrication steps are required. The optical fiber cabling, along with its cladding, is laid down on top of a first laminate layer, comprising a composite of silica fillers and a frictionless material like polytetrafluoroethylene (PTFE). Then a second layer of PTFE material with silica fillers and copper sheeting are placed on top of the PTFE with silica fillers composite. The PTFE material with silica fillers is flowable about the optical fibers, thus completely encasing them within an opaque sheath. This provides good optical isolation.
The laminate is then subjected to a laminating heat cycle, whose maximum temperature between approximately 350xc2x0 C. and 400xc2x0 C. is approximately fifty degrees above the PTFE with silica filler material""s melting point. The maximum pressure applied is between approximately 1,500 and 2,000 psi. The process completely embeds the optical fibers within the laminate, surrounded by the PTFE material with silica fillers. These optical fibers can then be used for optical signal transmissions within the laminate and the chip. The optical fibers are kept taut during the laminating procedure to provide accurate optical alignment. The laminate can also include electrical, in one example copper, lines for carrying electrical as well as optical signals.
The main advantages of this procedure and the article made therefrom are: optical fiber cables are commercially available in different sizes and there is no significant change in the lamination procedure for the BGA laminate by incorporating these optical fibers. Therefore, the resultant product is cost effective. Contrasting the above method of cable embedding with that of waveguide embedding, it is observed that embedding waveguides requires a significant development program and changes in manufacturing procedures. The optical fibers of this inventive article are surrounded with PTFE material with silica fillers, which is opaque. This automatically provides better optical isolation and shielding for the optical fiber signals.
In U.S. Pat. No. 6,244,756, issued to Bloom on Jun. 12, 2001, entitled APPARATUS AND METHOD BONDING OPTICAL FIBER, a fiber optic device is illustrated comprising embedded optical fibers and a deformable metal seal.
In U.S. Pat. No. 6,233,376, issued to Updegrove on May 15, 2001, entitled EMBEDDED FIBER OPTIC CIRCUIT BOARDS AND INTEGRATED CIRCUITS, a circuit board is illustrated in which optical fibers are embedded in at least one layer of the composite laminate. That circuit board is structurally different from the invention, which provides greater optical alignment accuracy during the embedding and laminating procedure, and in which the fibers are surrounded by an opaque layer of PTFE material with silica fillers that optically isolates the fibers.
In U.S. Pat. No. 6,210,046, issued on Apr. 3, 2001 to Rogers et al for FIBER OPTIC CONNECTOR WITH MICROALIGNABLE LENS HAVING AUTOFOCUS FEATURE AND ASSOCIATED FABRICATION METHOD, a fiber optic connector and method of making same are described. The optical connector features a lens and fiber combination.
In U.S. Pat. No. 6,181,854, issued to Kojima et al on Jan. 30, 2001, entitled OPTICAL MODULE PACKAGED WITH MOLDED RESIN, an optical fiber is contained within a housing, comprising two halves adhesively bonded together.
In U.S. Pat. No. 6,048,107, issued on Apr. 11, 2000 to Pubanz, for CRYOGENIC OPTICAL/ELECTRICAL INTERCONNECT MODULE, a cryogenic module containing optical fibers is illustrated. The optical fibers are adhesively bonded into a V-groove of a connector.
In U.S. Pat. No. 5,562,838, issued to Wojnarowski et al on Oct. 8, 1996, entitled OPTICAL LIGHT PIPE AND MICROWAVE WAVEGUIDE INTERCONNECTS IN MULTICHIP MODULES FORMED USING ADAPTIVE LITHOGRAPHY, an optical waveguide structure is formed within a substrate to provide a high-density interconnection.
In U.S. Pat. No. 5,006,201, issued to Kaukeinen on Apr. 19, 1991, for METHOD OF MAKING A FIBER OPTIC ARRAY, a substrate is shown having a plurality of stacked rows of fiber optic cables contained in the substrate by a glass top cemented thereto.
In U.S. Pat. No. 4,998,159, issued to Shinohara et al on Mar. 5, 1991, entitled CERAMIC LAMINATED CIRCUIT SUBSTRATE, a ceramic substrate is masked using fiber-containing green sheets.
In U.S. Pat. No. 4,221,962, issued on Sep. 9, 1980 to Black et al, for FIBER-OPTIC MOISTURE SENSOR FOR COMPOSITE STRUCTURES, an optical glass fiber is shown embedded in a laminated composite panel.
In Japanese Publication No. 6034827, applied for by Naohisa and published on Feb. 10, 1994, a fiber optic feed-through structure is illustrated.
In Japanese Publication No. 5072134, applied for by Akira et al and published on Mar. 23, 1993, an optical waveguide biosensor system is illustrated.
It is an object of the present invention to provide a fabrication method and an article fabricated by the method, for an organic laminate with embedded optical fibers.
It is another object of the invention to provide an improved BGA laminate containing embedded optical fibers.
In accordance with one embodiment of the invention, there is provided an organic laminate structure for use in an optical-electronic component comprising a core, and a plurality of optically isolated, optic fiber cables disposed adjacent the core and sheathed in an opaque material comprising silica fillers and a frictionless material such as polytetrafluoroethylene (PTFE), the optically isolated optic fiber cables being embedded within the organic laminate structure.
In accordance with another embodiment of the invention, there is provided an organic laminate structure for use in an optical-electronic component comprising a core, and a plurality of optically isolated, optic fiber cables disposed adjacent the core and sheathed in an opaque material, the optically isolated, optic fiber cables being embedded in tension alignment within the organic laminate structure.
In accordance with yet another embodiment of the invention, there is provided a method of fabricating a laminate structure, comprising the steps of disposing a plurality of optical fibers within a laminate structure during a laminating procedure that comprises applying pressure and heat, flowing opaque, optically isolating sheathing material about the optical fibers during the laminating procedure, and maintaining the optical fibers in tension during the laminating procedure.